The risk is highest -- about two-fold higher -- in patients with the most severe psoriasis, says researcher Ole Ahlehoff, MD, PhD, a post-doctoral fellow in cardiology at Copenhagen University Hospital Gentofte, in Denmark.

"Our results underline the importance of considering patients with psoriasis as a high-risk population in terms of diabetes and [heart disease and stroke] risk. Screening for diabetes and cardiovascular disease risk factors in these patients is warranted," he says.

Diabetes is a well-known risk factor for heart disease and stroke. Previous studies have shown that people with psoriasis have twice the risk of heart attack, stroke, and death compared to people without the skin disorder, Ahlehoff says.

The findings were presented here at the annual meeting of the European Society of Cardiology.

Inflammation a Common Link

Psoriasis is a common inflammatory disease affecting about 125 million people worldwide, Ahlehoff says.

Diabetes shares an underlying inflammatory process, so it makes sense that psoriasis would be a risk factor for new-onset diabetes, he says.

To test the hypothesis, the researchers examined about 4.5 million Danish national health records that included information on office visits and use of medication by people who were 10 years old or older in 1997. People who already had psoriasis or diabetes were excluded.

Over the next 13 years, more than 52,000 people had psoriasis, of whom 6,784 had severe psoriasis.

People with psoriasis were 56% more likely to develop diabetes than people without the skin disorder. The risk was 49% greater for people with mild psoriasis and two times higher for people with severe psoriasis. Most cases were type 2 diabetes, Ahlehoff says.

The findings held true even after the researchers took into account other risk factors for diabetes.

Ahlehoff suggests people with psoriasis undergo annual testing for diabetes as well as for heart disease risk factors such as high blood pressure and high cholesterol.

American Heart Association spokeswoman Rose Marie Robertson, MD, of Vanderbilt University in Nashville, says the study doesn't show that psoriasis causes diabetes, just that there is a link between the two disorders.

"The association seems clear and the common theme appears to be inflammation," she says. "But it could be something else.

"The interesting question is whether there is a common genetic predisposition to inflammation that leads to both, or whether some other non-inflammatory factor links the two," Robertson says.

These findings were presented at a medical conference. They should be considered preliminary, as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.